1. Technical Field
The present invention relates to an optical photographing system. More particularly, the present invention relates to a compact optical photographing system applicable to electronic products.
2. Description of Related Art
In recent years, with the popularity of mobile products with camera functionalities, the demand of optical lens systems is increasing. The sensor of a conventional optical lens system is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical lens systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical lens systems featuring better image quality.
A conventional compact optical lens system employed in a portable electronic product mainly adopts a four-element lens structure or a five-element lens structure such as the one disclosed in U.S. Pat. No. 7,869,142 and the one disclosed in U.S. Pat. No. 8,000,031. Due to the popularity of mobile products with high-end specifications, such as smart phones and PDAs (Personal Digital Assistants), the pixel and image-quality requirements of the compact optical lens system have increased rapidly. However, the conventional four-element lens structure or five-element lens structure cannot satisfy the requirements of the compact optical lens system.
Although there are other conventional optical lens systems with six-element lens structure, such as the one disclosed in U.S. Publication No. 2012/0229917. However, the distribution of the refractive power of the optical lens system is improper, so that the total track length thereof cannot be reduced effectively. Furthermore, the surface curvature of the second lens element has limited ability for correcting the aberration of the optical lens system and reducing the sensitivity thereof. Therefore, the optical lens system is hard to apply to portable electronics featuring high image quality.